you can easily just check the given answers,or find the answer yourself.I teach you the second :)
since the point (1,1) is in the domain and the point (4,1) is not, for 1<=x<4 we have y=1. (number one if incorrect, we put it aside...)
the point (6,2) is not in the graph and that line (y=2) starts from to point (4,2) ... this means that the third one is not the answer...
so far,the answer is found,but you can do the same for the last two lines to make sure that we've found the correct answer.